As one of several available methods to localize the neural site of action of abused drugs it is proposed to determine where in the brain rats will work to cause direct drug microinjection. Lateral hypothalamus and ventral tegmental areas are two sites where intracranial drug self-administration has been reported, and additional studies will be designed to localize the region at which drug acts when injected into these sites. Localization will be done by varying injection site and comparing dose-effectiveness, by determining the spread of radioactively labelled drug, and by comparing behavioral effectiveness before and after neurotoxic lesions at the cannula tip.